[Simetrical]

This is a nice mod. Unfortunately, it crashed my site when this query was run repeatedly during a period of high load (23 times over, running between 78 and 208 seconds, as of just before I started killing them):

mysql> EXPLAIN SELECT a.*, au.*, post.userid, post.postid 
    ->                         FROM post AS post
    ->                         INNER JOIN award_user AS au ON (au.userid=post.userid)
    ->                         INNER JOIN award AS a ON (a.award_id=au.award_id)
    ->                         WHERE 1=1 
    -> 
    -> 
    ->                         GROUP BY au.issue_id
    ->                         ORDER BY au.issue_time DESC;
+----+-------------+-------+--------+---------------+---------+---------+-------------------------+-------+---------------------------------+
| id | select_type | table | type   | possible_keys | key     | key_len | ref                     | rows  | Extra                           |
+----+-------------+-------+--------+---------------+---------+---------+-------------------------+-------+---------------------------------+
|  1 | SIMPLE      | au    | ALL    | NULL          | NULL    | NULL    | NULL                    |   117 | Using temporary; Using filesort | 
|  1 | SIMPLE      | a     | eq_ref | PRIMARY       | PRIMARY | 2       | totalwar_vb.au.award_id |     1 | Using where                     | 
|  1 | SIMPLE      | post  | ref    | userid        | userid  | 4       | totalwar_vb.au.userid   | 25005 | Using where                     | 
+----+-------------+-------+--------+---------------+---------+---------+-------------------------+-------+---------------------------------+
3 rows in set (0.00 sec)

While I'm no MySQL expert, it seems that this attempts to copy the entirety of the post table to a temporary table, in my case about 1.5 million rows. I've tracked the query down to the showthread_query hook:

PHP Code:

        // Obtain list of awards for current user
        $alluserawards =  $db->query_read("
            SELECT a.*, au.*, post.userid, post.postid 
            FROM " . TABLE_PREFIX . "post AS post
            INNER JOIN " . TABLE_PREFIX . "award_user AS au ON (au.userid=post.userid)
            INNER JOIN " . TABLE_PREFIX . "award AS a ON (a.award_id=au.award_id)
            WHERE 1=1 
". iif((!empty($ids)), "AND post.postid IN (0" . $ids . ")") ."
". iif((!empty($cache_postids)), "AND post.postid IN (" . $cache_postids . ")") ."
            GROUP BY au.issue_id
            $awardsdisplayorder
        ");

        while( $ua = $db->fetch_array($alluserawards))
        {
            $userawardscache[$ua['userid']][$ua['issue_id']] = $ua;
        }
        $db->free_result($alluserawards); 


Apparently this fails to account for the possibility that $ids and $cache_postids are both empty. I have no idea why it would or would not be reasonable to account for that, because I don't know what either of those variables is, but at any rate, if they both are empty things are not very good. I've wrapped the whole thing in a conditional checking whether both are empty, just not setting anything if they both are. I'd appreciate any response.